Egg Shells

Mention that you use "eggshells" in your potting mix and your friends may think you are crazy or you cannot effort "Perlite". That is sad, because eggshells are a great additive and increase the calcium content in your potting mix.

Chemical analysis of "dry" eggshells show that eggshells contains about 94% (CaCO3) (Calcium Carbonate) and has a typical mass of 5.5 grams, (values can differ). Eggshells also contain phosphorus, magnesium and traces of sodium, potassium, zinc, manganese, iron, and copper.

However, Calcium is the main component, and we know Ca is important to plants because it helps with cell wall structure imperative for the strength of the plant. Be assured that as the eggshells break down, they'll nourish your orchids.

Orchids suffering from calcium deficiency are more susceptible to rot.

When comparing brown versus white eggs, a definitive difference in composition, especially in Calcium carbonate amounts may be hard to find. The color of the eggshells is nothing more than a result of a different breed.

How to use them? I crush the eggshells as much as I can, down to tiny pieces. However, I am told that some growers use coffee grinders to pulverize the shells. The smaller the pieces the faster eggshells decompose (breakdown) and must be replaced.

Alternative: Calcite (Limestone) or Dolomite.